In monitoring device installations, monitor settings are an important part of the overall installation process. This article focuses on the problems that are easy to occur in the monitor settings and the corresponding solutions.
Problems with the monitor settings: A large area of ​​moire is generated on the monitor screen.
Solution: The fault caused by short circuit and open circuit of the core wire of the video cable and the shielded cable. This type of failure occurs mostly on BNC connectors or other types of video connectors. That is to say, when such a fault phenomenon occurs, it is often not a problem of the signals of the entire system, but only the number of paths in which the joints are not good. As long as you carefully check these connectors one by one, you can solve them.
Problem 2 in the monitor settings: There are several splint interferences on the monitor screen.
Solution:
Most of this interference phenomenon occurs because there is a strong, high-frequency spatial radiation source near the transmission system, the front end of the system, or the central control room. Therefore, when the system is established, the surrounding environment should be understood, try to avoid or avoid the radiation source; when the radiation source cannot be avoided, the front end and the center equipment should be shielded, and the transmission line and pipeline should be made of steel pipe and well grounded.
Problem 3 in the monitor settings: A black bar or white bar appears on the monitor screen and scrolls up or down slowly.
Solution: To distinguish between the problem of power supply or the problem of ground loop, an easy way is to connect only one power supply to the control host, and if there is no problem, the camera output signal is not on the monitor. The interference phenomenon indicates that the control host has no problem. Next, use a portable monitor to connect to the video output of the front camera and check each camera one by one. If yes, the processing is performed. If not, the interference is caused by other reasons such as the ground loop.
Problem 4 in the monitor settings: Wood grain interference on the monitor.
Solution: The occurrence of this kind of interference will not overwhelm the normal image when it is slight, and the image will not be watched (or even destroy the synchronization) when it is serious. The causes of such failures are more complicated and complicated. There are roughly the following reasons:
1) The quality of the video transmission line is not good, especially the shielding performance is poor (the shielding net is not a good quality copper wire mesh, or the shielding mesh is too thin to prevent shielding). The line resistance of such a video line is too large, so that a large attenuation of the signal is also a cause of aggravation of the failure.
2) The characteristic impedance of this type of video line is not 75 ohms as the main parameter. Exceeding the specification is also one of the causes of the failure.
Since the above-mentioned interference phenomenon is not necessarily a failure caused by a bad video line, the cause of such a failure is accurate and prudent in judging. Only when the other possibilities are excluded can we consider from the perspective of the video line. If it is really a cable quality problem, the best way is to replace all of this cable and replace it with a cable that meets the requirements. This is the best way to solve the problem completely.
3) There is a strong source of interference near the system. This can be judged by investigation and understanding. If this is the case, the solution is to strengthen the shielding of the camera and ground the pipeline of the video cable.
Problem 5 in the monitor settings: Several vertical bar interferences are generated on the monitor screen.
Solution: This is due to the impedance mismatch caused by the characteristic impedance of the video transmission line being 75 ohms. It can also be said that this interference phenomenon is caused by the fact that the characteristic impedance and distribution parameters of the video cable are not in compliance with the requirements. Generally, it is solved by the method of connecting the resistor at the beginning or connecting the resistor with the terminal. In addition, it is worth noting that when the video transmission distance is short (usually within 150 meters), the above-mentioned interference phenomenon may not occur with the video cable having the above-mentioned impedance mismatch and excessive distribution parameters. The fundamental way to solve the above problems is to ensure the quality of the video cable, and if necessary, the cable should be sampled.
The above is the reason analysis of the five problems that are easy to appear in the monitor setting process and the corresponding solutions, I hope to help everyone.
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